The present invention relates to a recording paper size discriminating structure callable or discriminating the size of the recording paper contained in the recording paper cassette which is installed at a paper feeding portion or an imaging apparatus so that recording paper can be fed from the recording paper cassette to the image forming portion of the imaging apparatus to Form images on it.
Conventionally, an imaging apparatus such as a copy machine, a printer, a facsimile machine and the like are known which are characterized in that an image formation is carried out by use of plain paper being cut in a predetermined size.
In such an imaging apparatus, recording papers (plain papers) are usually contained or accommodated in a recording paper cassette so as to be piled up or stacked in it. Namely, the recording paper cassette is detachably installed at a paper feeding portion of the imaging apparatus. Recording paper is fed one by one from the recording paper cassette to an image forming portion of the imaging apparatus.
Recording papers are classified into a plurality of predetermined sizes. Therefore, a typical imaging apparatus is constituted in such a manner that a plurality of recording cassettes which are respectively made in the different sizes or recording papers can be simultaneously installed so as to correspond to these various recording paper sizes. Especially, this kind of constitution is essential for recent copy machines.
However, the recording paper cassettes are normally made to have the same outer configuration in order to mate with a common cassette coupling portion formed on the imaging apparatus. On the other hand, their inside spaces are partitioned exclusively for fitting any one of respective recording paper sizes.
For this reason, users need to prepare a significant number of recording paper cassettes equal to the number of recording paper sizes they intend to use. If they further want to use recording paper or a different size which has not been used, a recording paper cassette corresponding to this size needs to be newly prepared or added. As a result many recording paper cassettes suited for respective different recording paper sizes are required even though their outer configurations are the same which is unreasonable.
Moreover, in such an imaging apparatus equipped with a recording paper cassette, especially in the ease where a plurality of recording paper cassettes are simultaneously installed, it is necessary to discriminate currently usable recording paper sizes; i.e. recording paper sizes contained in the recording paper cassettes simultaneously installed in the imaging apparatus at that time, and feed recording paper of a designated size from Lie corresponding recording paper cassette.